The efficient utilization of energy is important in any industrial process, and it is well known to recover heat from a process gas prior to exhausting the gas back into the environment. The production of an alcohol from corn or other biomass produces a moist solids byproduct (wet cake) which can be partially dried in a rotary drum or steam tube dryer before being further processed as animal feed or fertilizer. The dryer exhaust gas contains heat and moisture that can be captured before being released to the atmosphere.
U.S. Pat. No. 3,131,035 describes the recycling of dryer exhaust gas through an incinerator, with a portion of the incinerated gas being exhausted to atmosphere only after passing through a heat exchanger to pre-heat the bulk dryer exhaust gas travelling into the incinerator. That patent also teaches the extraction of heat from the exhaust gas via a heat exchanger using a liquid extracted from the material being dried. The heated liquid is then concentrated in an evaporator which produces both a concentrated liquid for reuse in the feedstock stream and a vapor that is condensed and disposed of in any suitable manner.
United States Patent Application Publication No. US 2011/0108409 A1 describes an ethanol production system where the exhaust stream from a steam dryer is directed to the bottom of a distillation column in order to heat the distillation column and to scrub the exhaust stream.
U.S. Pat. No. 8,429,832 describes the use of waste heat from a steam dryer being captured and used in the production of steam for the dryer.
International Application Publication No. WO 2013/144438 A1 describes the use of flue gas from a combustion device being used to heat a liquid to be concentrated in a multiple-effect evaporation plant.
Further improvements in the energy efficiency of such industrial processes are desired.